firlbq.asm

实现一个40阶的fir低通滤波器

			.title		"firlbq.asm"
			.mmregs
			.bss		y,1
k_fir_bffr			.set		40
pa0 				.set		0
pa1					.set		1
fir_coff_table		.usect		"fir_coff",40
d_data_buffer		.usect		"fir_bfr",40
					.data
coff_fir_start:     .word      -7*32768/10000,   3*32768/10000
					.word      14*32768/10000,   10*32768/10000
					.word      -16*32768/10000,  -38*32768/10000
					.word      -8*32768/10000,   64*32768/10000
					.word      81*32768/10000,   30*32768/10000
					.word      -169*32768/10000,  -118*32768/10000
					.word      162*32768/10000,  353*32768/10000
					.word      83*32768/10000,   -515*32768/10000
					.word      -689*32768/10000,   247*32768/10000
					.word      2051*32768/10000,  3523*32768/10000
					.word      3523*32768/10000,  2051*32768/10000
					.word      247*32768/10000,   -689*32768/10000
					.word      -515*32768/10000,   83*32768/10000
					.word      353*32768/10000,   162*32768/10000
					.word      -118*32768/10000,   -169*32768/10000
					.word      -30*32768/10000,   81*32768/10000
					.word      64*32768/10000,   -8*32768/10000
					.word      -38*32768/10000,   -16*32768/10000
					.word      10*32768/10000,   14*32768/10000
					.word      3*32768/10000,   -7*32768/10000
					.text
					.def    fir_int
					.def    fir_task

fir_int:      ssbx      frct
              stm       #fir_coff_table,ar5
              rpt       #k_fir_bffr-1
              mvpd		#coff_fir_start,*ar5+
              stm		#d_data_buffer,ar4
              rptz		a,#k_fir_bffr-1
              stl		a,*ar4+
              stm		#(d_data_buffer+k_fir_bffr-1),ar4
              stm		#(fir_coff_table+k_fir_bffr-1),ar5					 
			  stm 		#-1,ar0
			  ld		#d_data_buffer,dp
			  portr		pa1,@d_data_buffer
fir_task:	  stm		#k_fir_bffr,bk
			  rptz		a,#k_fir_bffr-1
			  mac		*ar4+0%,*ar5+0%,a
			  sth		a,@y
			  portw		@y,pa0
			  bd		fir_task
			  portr		pa1,*ar4+0%
			  .end